Long Zheng has come up with a simple idea on how this this can be solved. If you keep the capacitive button pressed for more than a specified time (the circle keeps getting filled meanwhile) , the Bing app launches otherwise you return to whatever you were doing. This design is similar to the one found in the MetroTwit app. Zheng would have liked to do the same for the 'back' button but that action is used for multi-tasking in Mango.
[Source]
